Relational DBMSs are currently the dominant database technology. The OODBMS has also become the favored system for financial and telecommunications applications. Although the OODBMS market is still same. The OODBMS continues to find new application areas, such as the World Wide Web. Some industry analysts expect the market for the OODBMSs to grow at over 50% per year, a rate faster than the total database market.

However, their sales are unlikely to overtake those of relational systems because of the wealth of businesses that find RDBMSs acceptable, and because businesses have invested to much money and resources in their development that change is prohibitive.

Until recently, the choice of DBMS seemed to be between the relational DBMS and the object-oriented DBMS. However, many vendors of RDBMS products are conscious of the threat and promise of the OODBMS. They agree that traditional relational DBMSs are not suited to the advanced application. The most obvious way to remedy the shortcomings of the relational model is to extend the model with these types of feature.

This is the approach that has been taken by many extended relational DBMSs, although each has implemented different combinations of features. Thus there is no single extended relational model rather, there are a variety of these models, whose characteristics depends upon the way and the degree to which extensions were made. However, all the models do share the same basic relational tables and query language, all incorporate some concept of 'object, and some have the ability to store methods (or procedures or triggers), as well as data in the database.

In a four-quadrant view of the database world, as illustrated in the figure, the lower-left quadrant are those applications that process simple data and have no requirements for querying the data.

These types of application, for example standard text processing packages such as Word,

WordPerfect, and Frame maker, can use the underlying operating system to obtain the essential DBMS functionality of persistence. In the lower-right quadrant are those applications that process complex data but again have no significant requirements for querying the data. For these types of application, for example computer-aided design packages, an OODBMS may be an appropriate choice of DBMS.

In the top-left quadrant are those applications that process simple data and also have requirements for complex querying. Many traditional business applications fall into this quadrant and an RDBMS may be the most appropriate DBMS.

Finally, in the top-right quadrant are those applications that process completed data and have complex querying requirements. This represents many of the advanced database applications and for these applications an ORDBMS may be the appropriate choice of DBMS.

Advantages and Disadvantages of ORDBMSS

ORDBMSs can provide appropriate solutions for many types of advanced database applications. However, there are also disadvantages.

Advantages of ORDBMSs

There are following advantages of ORDBMSs:

Reuse and Sharing: The main advantages of extending the Relational data model come from reuse and sharing. Reuse comes from the ability to extend the DBMS server to perform standard functionality centrally, rather than have it coded in each application.

Increased Productivity: ORDBMS provides increased productivity both for the developer and for the, end user

Use of experience in developing RDBMS: Another obvious advantage is that .the extended relational approach preserves the significant body of knowledge and experience that has gone into developing relational applications. This is a significant advantage, as many organizations would find it prohibitively expensive to change. If the new functionality is designed appropriately, this approach should allow organizations to take advantage of the new extensions in an evolutionary way without losing the benefits of current database features and functions.

Disadvantages of ORDBMSs

The ORDBMS approach has the obvious disadvantages of complexity and associated increased costs. Further, there are the proponents of the relational approach that believe the· essential simplicity' and purity of the .relational model are lost with these types of extension.

ORDBMS vendors are attempting to portray object models as extensions to the relational model with some additional complexities. This potentially misses the point of object orientation, highlighting the large semantic gap between these two technologies. Object applications are simply not as data-centric as relational-based ones.